Adventure Time: Fionna and Cake is an American adult animated television series developed by Adam Muto, based on the Cartoon Network series Adventure Time, which was created by Pendleton Ward. Unlike Adventure Time, the show is made for a young adult audience. The third series in the franchise, it premiered via the streaming service Max on August 31, 2023. It was later renewed for a second season.

The series focuses on the titular characters, Fionna and Cake the Cat, alternative versions of main characters Finn the Human and Jake the Dog from the original series, along with the Ice King as his human form Simon Petrikov. The series is executive produced by Muto, who had served as showrunner for the latter half of Adventure Time and oversaw production of the Distant Lands specials, as well as Fred Seibert and Sam Register.